1. Field of Invention
The present invention related to a charging device capable of providing inrush current protection, and more particularly, to a charging device capable of providing inrush current protection when the system is powered on.
2. Description of Related Art
With the tide of electronic devices turning towards smaller and lighter, electronic system, such as the mobile phones, the cameras and the personal digital assistants (PDAs), are used more and more frequently in daily life. For helping the users to carry the electronic system at anytime and anywhere, the electronic system are all equipped with rechargeable batteries for providing desired electric power when the electronic system operates. In general, when the electric power of the rechargeable batteries are exhausted, the electronic system can perform the recharging procedures for the rechargeable batteries by connecting to an external power source through a connecting line, such as an universal serial bus (USB), so as to maintain effective operation of the electronic system.
When the electronic system is connected to an external power source, an internal power control circuit of the electronic system switches the power source from the rechargeable battery to the external power source. At such a time, the external power source not only supplies sufficient power to the electronic system for normal operation, but also enables the recharging procedures for the rechargeable battery to replenish consumed energy of the rechargeable battery until the electronic system disconnects from the external power source.
However, when the external power source is connected to the electronic system to charge the electronic system, an instant great inrush current occurs, which impacts the internal circuits of the electronic system before the electronic system is stable. As a result, the circuit components of the electronic system might be damaged by the instant great inrush current.
Therefore, there is a need for a new device or a new circuit which can prevent the instantaneous large current from damaging the system when the system starts on.